Tank made of a composite material

ABSTRACT

A tank including a single tank body made as a single piece of a composite material using a closed molding process with a first portion of the tank body having an outside surface corresponding to a first molding surface of a first mold and a second portion of the tank body having an outside surface corresponding to a second molding surface of a second mold. The tank body has an opening disposed therein with the opening being substantially smaller than the tank body. The tank further includes a fitting member mounted to a portion of the tank body surrounding the opening.

This application is a divisional of U.S. patent application Ser. No.13/793,489, now U.S. Pat. No. 9,446,898, filed on Mar. 11, 2013 andentitled Tank Made Of A Composite Material And Closed Molding ProcessFor Manufacturing The Same, which in turn claims priority to CanadianPatent Application Serial No. 2805826, entitled Tank Made Of A CompositeMaterial And Closed Molding Process For Manufacturing The Same, filed onFeb. 11, 2013 in the name of inventor Glen Aylward. The entire contentsof both of these documents are incorporated herein by reference.

FIELD

The present invention relates to tanks, and more particularly to tanksmade of a composite material and a closed molding process formanufacturing the same.

BACKGROUND

Tanks used in numerous applications such as, for example, oil tanks,water tanks and compressor tanks are nowadays made of a compositematerial such as, for example, a fiberglass composite material. Use of acomposite material provides a light weight and substantially corrosionresistant tank.

State of the art composite material tanks are made using a chopper gun.Unfortunately, this process exposes the operator of the chopper gun aswell as the environment to fine particles and volatile resin componentsduring operation of the chopper gun and, furthermore, exposes theuncured resin to the atmosphere. Further disadvantages are anunappealing finish of the outside surface of the tank as well asinconsistent quality of the tank depending on the skill of the operator.

Another process for producing composite material parts is the vacuuminfusion process, which is carried out within a closed molding system,i.e. the void between a sealed bag and a mold, or between two sealedmolds. This process is capable of producing composite material parts ofhigh and consistent quality.

Typically, composite material tanks are made in two halves which arejoined together using an adhesive, resulting in a bond linesubstantially weakening the tank.

It is desirable to provide a method for manufacturing a compositematerial tank in substantially a single piece using a closed moldingprocess.

It is also desirable to provide a composite material tank that ismanufactured in substantially a single piece using the closed moldingprocess.

SUMMARY

Accordingly, one object of the present invention is to provide a methodfor manufacturing a composite material tank in substantially a singlepiece using a closed molding process.

Another object of the present invention is to provide a compositematerial tank that is manufactured in substantially a single piece usingthe closed molding process.

According to one aspect of the present invention, there is provided amethod for manufacturing a tank. A first mold having a first moldingsurface corresponding to a first portion of an outside surface of thetank is provided. A second mold having a second molding surfacecorresponding to a second portion of the outside surface of the tank isprovided. The first portion and the second portion form the outsidesurface of the tank having an opening disposed therein. A mold releaseagent is disposed onto the first and second molding surface. A moldingbladder is provided. An outside surface of the molding bladder wheninflated substantially corresponds to an inside surface of the tankhaving the opening disposed therein. A reinforcement material isdisposed onto one of the molding bladder and the molding surfaces. Thefirst and the second mold are combined in a sealed fashion. The firstand the second mold have accommodated therebetween the reinforcementmaterial and the molding bladder. A molding space between the moldingbladder and the combined first and second mold is sealed. The moldingspace contains the reinforcement material. The molding space isevacuated. The evacuated molding space is then filled with a resin. Theresin is cured to form a wall of the tank. The molding bladder isdeflated and removed through the opening. The first and the second moldare separated and removed from the tank.

According to another aspect of the present invention, there is provideda tank. The tank comprises a single tank body made as a single piece ofa composite material using a vacuum infusion process with a firstportion of the tank body having an outside surface corresponding to afirst molding surface of a first mold and a second portion of the tankbody having an outside surface corresponding to a second molding surfaceof a second mold. The tank body has an opening disposed therein with theopening being substantially smaller than the tank body. A fitting memberis mounted to a portion of the tank body surrounding the opening.

An advantage of the present invention is that it provides a method formanufacturing a composite material tank in substantially a single pieceusing a closed molding process.

A further advantage of the present invention is that it provides acomposite material tank that is manufactured in substantially a singlepiece using the closed molding process.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the present invention are described below withreference to the accompanying drawings, in which:

FIGS. 1a to 1d are simplified block diagrams illustrating a perspectiveview, a front view, a top view, and a side view, respectively, of adomestic oil tank made of a composite material according to oneembodiment of the invention;

FIG. 1e is a simplified block diagram illustrating a perspective view ofa tank body made of a composite material according to one embodiment ofthe invention;

FIGS. 2a to 2c are simplified block diagrams illustrating a perspectiveview, a cross sectional view, and a top view, respectively, of a firstmold used in a closed mold vacuum infusion process according to oneembodiment of the invention;

FIG. 2d is a simplified block diagram illustrating a cross sectionalview of a second mold used in the closed mold vacuum infusion processaccording to one embodiment of the invention;

FIG. 2e is a simplified block diagram illustrating a cross sectionalview of a molding bladder used in the closed mold vacuum infusionprocess according to one embodiment of the invention;

FIG. 2f is a simplified block diagram illustrating a cross sectionalview of the first mold with the molding bladder used in the closed moldvacuum infusion process according to one embodiment of the invention;

FIG. 2g is a simplified block diagram illustrating a cross sectionalview of the combined first and second mold with the molding bladder usedin the closed mold vacuum infusion process according to one embodimentof the invention;

FIG. 2h is a simplified block diagram illustrating the resin flow in across sectional view of the combined first and second mold with themolding bladder used in the closed mold vacuum infusion processaccording to one embodiment of the invention;

FIG. 2i is a simplified block diagram illustrating in a cross sectionalview the removal of the molding bladder from the tank body in the closedmold vacuum infusion process according to one embodiment of theinvention;

FIGS. 3a and 3b are simplified block diagrams illustrating in crosssectional views insertion and mounting of the fitting member in theclosed mold vacuum infusion process according to one embodiment of theinvention; and

FIG. 4 is a simplified block diagram illustrating a top view of a firstmold used in a closed mold vacuum infusion process according to anotherembodiment of the invention.

DETAILED DESCRIPTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, certain methods andmaterials are now described.

While embodiments of the invention will be described for manufacturingan oil tank for domestic use, it will become evident to those skilled inthe art that the embodiments of the invention are not limited thereto,but are also adaptable for manufacturing various other types of tankssuch as, for example, water tanks, compressor tanks, and propane tanksfor domestic use as well as industrial use. Furthermore, it will becomeevident to those skilled in the art that the embodiments of theinvention are not limited to the employment of fiberglass asreinforcement material, but are adaptable to the use of various otherreinforcement materials such as, for example, carbon fiber.

Referring to FIGS. 1a to 1e , a domestic oil tank 100 made of acomposite material according to one embodiment of the invention isprovided. The tank 100 comprises a single tank body 102 made as a singlepiece of a composite material using a closed molding process accordingto one embodiment of the invention described hereinbelow. The tank body102 has an opening 110 disposed therein. In one case the opening 110 issubstantially smaller than the tank body 102 and is covered by a fittingmember 104 mounted to a portion of the tank body 102 surrounding theopening 110 with the fitting member 104 having, for example, fittings106 for being connected to: a fill pipe; a vent pipe; a supply pipe; anda level gauge. The tank 100 can also comprise a base member 108 mountedto a bottom portion of the tank body 102.

The tank body 102 is designed to enable manufacture using a closed moldvacuum infusion process according to one embodiment of the inventionprovided hereinbelow with reference to FIGS. 2a to 2i . A first portionof the tank body 102 has an outside surface 114A corresponding to afirst molding surface 204A of a first mold 202A and a second portion ofthe tank body 102 has an outside surface 114B corresponding to a secondmolding surface 204B of a second mold 202B. The outside surfaces 114Aand 114B are designed—based on standard molding technology—such thatduring the molding process the molds 202A and 202B are in contact atseam 112 and can be separated and removed from the outside surfaces 114Aand 114B after curing of the tank body 102. The outside surfaces 114Aand 114B illustrated in FIG. 1e are symmetric with respect to the seam112. As is evident to one skilled in the art, while facilitating thedesign and manufacture of the molds 202A, 202B, it is not necessary forthe outside surfaces 114A and 114B to be symmetric, i.e. the outsidesurfaces 114A and 114B can be of different shape as long as they can becombined at the seam 112.

Referring to FIGS. 2a to 2i a closed mold vacuum infusion processaccording to one embodiment of the invention is provided. Based on theoutside surfaces 114A and 114B of the tank body 102, molds 202A and 202Bare designed and provided. The molds 202A and 202B can be designedsimultaneously with the outside surfaces 114A and 114B of the tank body102. The molds 202A, 202B comprise the molding surfaces 204A, 204Bsurrounded by sealing flanges 206A, 206B with a portion 208A, 208B beingrecessed corresponding to the opening 110. Flange seal 212 is disposedon the flange 206A to provide seal space 214 therebetween which is, inone case, sealed in an airtight fashion. Furthermore, opening seals216A, 216B are disposed on the recessed flange portions 208A, 208B toprovide seal spaces 218A, 218B, respectively. Evacuation port 222 isdisposed in flange 206A and designed for being connected to a vacuumpump. The molds 202A, 202B can be made of a fiberglass material havingsufficient wall thickness to provide sufficient rigidity to the molds202A, 202B for executing the molding process absent deformation of thesame. Of course, other materials such as metals are also applicable, butthe fiberglass material may be useful for providing sufficient rigiditywhile being lightweight for facilitating handling of the molds.

In a first step of the closed mold vacuum infusion process the moldingsurfaces 204A, 204B are coated with a release agent to aid in theseparation of the molding surfaces 204A, 204B from the outside surfaces114A and 114B of the tank body 102 after curing and to reduceimperfections in the molding surfaces 204A, 204B in order to providesmooth outside surfaces 114A and 114B. The molding surfaces 204A, 204Bcan be coated with a thin layer—approximately 0.5 mm—of ENGUARD FRSERIES FIRE RETARDANT ISO/NPG GELCOAT.

Next, the reinforcement material is placed onto the molding surfaces204A, 204B. In one case, the reinforcement material is a layer offiberglass fabric. A fiberglass fabric with a thermo set powder in theglass such as, for example, UM-720 fiberglass fabric, can be employed.The fiberglass fabric can preformed to correspond to the moldingsurfaces 204A, 204B such that each molding surface is covered with onelayer of fabric 220A, 220B and such that the fabric layer 220A disposedin mold 202A is protruding the mold 202A a predetermined distance D—forexample, 3 inches—producing an overlap of the layers 220A, 220B of thesame distance, as illustrated in FIGS. 2b and 2g . The predetermineddistance D is designed to provide sufficient strength to the tank body102 at the seam 112 depending, for example, on the size of the tank body102 and an inside pressure range the tank body 102 is designed towithstand. Optionally, more than one layer of the reinforcement materialis disposed on each molding surface. Further optionally, the layers aredesigned such that different layers overlap at a different location inorder to further increase the strength of the tank body 102.Alternatively, other reinforcement materials are employed such as, forexample, carbon fiber or various organic fibers or combinations thereofknown to one skilled in the art. Optionally, the fabric layers 220A,220B are secured to the respective mold surfaces 204A, 204B using acommercially available spray adhesive such as, for example, a styrenebased spray adhesive for temporarily bonding light and medium weightfiber reinforcements.

After placement of the reinforcement material, molding bladder 302 isplaced into the mold 202A onto reinforcement layer 220A and inflated toa pressure such that an outside surface 304 of the molding bladdercorresponds approximately to an inside surface of the tank body 102 andis capable of holding the reinforcement layer 220A in place, asillustrated in FIG. 2f , as well as the reinforcement layer 220B aftercombining the molds 202A and 202B in a later step. Alternatively, thereinforcement layer 220B is placed onto the molding bladder 302 insteadof being placed into the mold 202B.

The molding bladder 302, illustrated in FIG. 2e , is designed such thatduring the molding process an outside surface 304 of the inflatedmolding bladder 302 substantially corresponds to an inside surface ofthe tank body 102 having the opening 110 disposed therein. Furthermore,the molding bladder 302 comprises a sealing extension 306 for providing,in concert with the opening seals 216A, 216B, an airtight seal betweenthe bladder 302 and the molds 202A, 202B. Resin injection conduit 318 isdisposed inside the molding bladder 302 and connected to resin injectionport 316 and resin injection aperture 320. The molding bladder 302 isinflated by providing a compressed fluid such as compressed air viainflating port 308. Evacuating conduit 311 is disposed in the sealingextension 306 and connected to evacuating openings 312 and 314 andevacuating port 310 for being connected to a vacuum pump. The moldingbladder 302 is made of a flexible material such as, for example, asilicone rubber material for enabling re-use of the same. The evacuatingconduit 311 and the resin injection conduit 318 are made of a flexiblematerial such as, for example, a silicone rubber material or,alternatively, a rigid material.

After placing and inflating the molding bladder 302, the molds 202A,202B are combined and sealed in a substantially airtight fashion byevacuating the seal space 214 via evacuation port 222 to a predeterminedvacuum, such as a low vacuum of approximately 3000 Pa. Alternatively,the molds 202A, 202B are combined and sealed in a substantially airtightfashion by clamping the flanges using, for example, a plurality ofclamps. Further alternatively, inflation of the molding bladder 302 isomitted in case the fabric layers 220A, 220B are secured to therespective mold surfaces 204A, 204B using, for example, a Tack SprayAdhesive and the sealing extension 306 is designed to provide a properseal absent inflation of the molding bladder 302.

Further alternatively, the molding bladder 302 is inflated to net shapeand the reinforcement material is then disposed onto the outside surface304 of the molding bladder 302 using the Tack Spray Adhesive. Themolding bladder 302 with the reinforcement material is then placed ontomolding surface 204A of mold 202A followed by placement of mold 202Bthereupon. Provision of the reinforcement material onto the outsidesurface of the molding bladder 302 removes the restriction of providingthe reinforcement material in two sections with each sectionsubstantially corresponding to one of the molding surfaces 204A, 204Bresulting in an overlap in proximity to the seam 112.

Next, molding space 322 between the outside surface 304 of the moldingbladder 302 and the molding surfaces 204A, 204B, containing thereinforcement layers 220A, 220B, as well as seal spaces 218A, 218B areevacuated to a predetermined vacuum, such as a low vacuum ofapproximately 3000 Pa via evacuating openings 314 and 312, respectively.Evacuation via evacuating opening 312 provides a substantially airtightseal between the recessed flange portions 208A, 208B of the molds 202A,202B and the sealing extension 306 of the molding bladder 302, whileevacuation via evacuating opening 314 evacuates the molding space 322including spaces between fibers of the reinforcement material 220A, 220Bto ensure penetration of the same by the resin provided in the followingstep. The molding bladder 302 can be designed such that the outsidesurface 304 of the molding bladder 302 substantially corresponds to theinside surface of the tank body 102 when the molding space 322 isevacuated to the low vacuum of approximately 3000 Pa.

Once the molding space 322 is evacuated to the predetermined vacuum, theresin—for example, a vinyl ester resin or epoxy resin—is injected intothe molding space 322 via resin injection aperture 320 while evacuationof the molding space 322 is continued. The resin can be ISO FLAMERETARDANT DION FR 7767-80. The resin injected via resin injectionaperture 320 is then drawn by the vacuum throughout the molding space322 including the spaces between fibers of the reinforcement material220A, 220B towards the evacuating opening 314 located at a substantiallyopposite end portion of the molding space 322 from the location of theresin injection aperture 320, as indicated by the arrows in FIG. 2h ,until the resin has reached the evacuating opening 314 or,alternatively, until the resin is drawn through evacuating conduit 311and evacuating port 310 into, for example, a resin trap interposedbetween a vacuum pump and evacuating port 310. Optionally, a pluralityof resin injection apertures are provided, with all resin injectionapertures being placed substantially opposite to the evacuating opening314 or with some resin injection apertures being placed between thelocation of the resin injection aperture 320 and the evacuating opening314, for example, placed in a midsection of the molding bladder 302.Further optionally, the resin is injected into the molding space 322under pressure with the pressure being determined such that the moldingbladder 302 can withstand the same absent deformation. Furtheroptionally, the pressure in the molding bladder 302 is increased suchthat the molding bladder 302 is capable to withstand the pressure of theinjected resin absent deformation.

During the curing process, the temperature of the resin continuouslyincreases while the resin progresses through a gel stage followed by ahardening stage until a peak temperature—called “peak exotherm”—isreached. The peak exotherm temperature depends on the resin and thelaminate—or wall—thickness with the peak exotherm temperature beinghigher with increasing thickness. The temperature can be measured inproximity to the location of the resin injection aperture 320 since atthis location the resin starts to gel first due to the increased wallthickness, i.e. mass. The temperature of the resin is measured using,for example, a commercially available infrared gun, enabling measurementthrough the molding bladder 302 with the molding bladder 302 being madeof a transparent material.

Once the peak exotherm temperature is reached, the molding bladder 302is deflated and removed through the opening 110, as illustrated in FIG.2i . The opening 110 illustrated in FIG. 1e is designed to accommodatethe fitting member 104 containing all the fittings 106 and, therefore,is larger than needed to remove the molding bladder 302. The size of theopening 110 needed for removing the molding bladder 302 depends on theshape, size, and material of the molding bladder 302.

After removal of the molding bladder 302 the seal space 214 is vented inorder to separate the molds 202A and 202B and to remove the same fromthe tank body 102, thus releasing the tank body 102.

The reinforcement layers 220A, 220B can be preformed to correspond tothe molding surfaces 204A, 204B and to have a constant thicknessthroughout for providing, in concert with the outside surface 304 of themolding bladder 302, a constant wall thickness of the tank body 102,with the exception of the location of the overlap of the reinforcementlayers 220A, 220B. The wall thickness of the tank body 102 isapproximately the same as the thickness of the reinforcement layers220A, 220B and double at the location of the overlap of thereinforcement layers 220A, 220B. The contact of the reinforcement layers220A, 220B with the outside surface 304 of the molding bladder 302allows the resin to transfer evenly throughout the reinforcement layers220A, 220B. With the preformed reinforcement layers 220A, 220B having asubstantially constant fiber-to-void ratio the amount of resin used formanufacturing the tank body 102 is substantially the same resulting in asubstantially repeatable process for producing tank bodies 102 havingsubstantially same dimensions, weight, and strength.

Fitting member 104 comprising fittings 106 is then mounted in a sealedfashion to the tank body 102. The fitting member 104 is, for example,manufactured using a standard vacuum infusion process with the fittings106 being commercially available Fiberglass Reinforced Plastic (FRP)fittings mounted to previously drilled openings in the fitting member104 using an epoxy adhesive. As illustrated in FIG. 3a , the fittingmember 104 is passed through the opening 110 with fitting member 104 andthe opening 110 having a corresponding elongated shape. Inside the tankbody 102, the fitting member 104 is then turned and inserted into theopening 110 such that flange 105 of the fitting member is in contactwith a portion of the inside surface of the tank body 102 surroundingthe opening 110, as illustrated in FIG. 3b . The fitting member 104 canbe mounted to the tank body 102 using an adhesive such as, for example,an epoxy adhesive, which is disposed onto the flange 105 prior insertioninto the tank body 102. The epoxy adhesive employed can be PLIOGRIPEPDXY 5760B. After insertion into the opening 110 the flange 105 of thefitting member 104 is pushed towards the tank body 102 and hold in placeduring curing of the adhesive, for example, by providing compressed airinto the tank body 102 at a pressure of, for example, 35000 Pa aboveoutside pressure. The flange is designed to be sufficiently wide forproviding a proper seal when mounted to the tank body 102 having, forexample, a width of approximately 50 mm.

Alternatively, the fitting member 104 is mounted to the outside surfaceof the tank body 102, for example, when the tank 100 is designed forbeing operated at an inside pressure that is below a pressure theoutside of the tank 100 is exposed to.

Finally, the base member 108—for example, manufactured using a standardvacuum infusion process—is mounted to a bottom portion of the tank body102 using, for example, an epoxy adhesive.

The closed mold vacuum infusion process according to one embodiment ofthe invention has been applied for manufacturing a 1000 l domestic oiltank, illustrated in FIGS. 1a to 1e , having: height H of 1229 mm;length L of 1715 mm; width W of 602 mm; and wall thickness of 4.8 mm.The opening 110 has a length of 787 mm and a width of 203 mm and wasdesigned to accommodate the fitting member 104 containing all thefittings 106, i.e. the opening 110 is larger than needed for removingthe molding bladder 302.

As is evident the closed mold vacuum infusion process according to oneembodiment of the invention is adaptable for manufacturing compositematerial tank bodies having various shapes and sizes.

Referring to FIG. 4, another embodiment of the closed mold vacuuminfusion process is provided. Here, the tank body is designed such thatthe opening 410 for removing the molding bladder is placed in themolding surface 404A of a single mold 402A. The processing steps aresubstantially the same. A reinforcement layer, having an openingcorresponding to the opening 410, is placed into the mold 402A. Themolding bladder is then placed onto the reinforcement layer with thesealing extension being accommodated in the opening 410 and inflated.Another reinforcement layer is then placed onto the inflated moldingbladder followed by a second mold associated with the mold 402A. Thefollowing steps are then executed in a same fashion as describedhereinabove.

The present invention has been described herein with regard to certainembodiments. However, it will be obvious to persons skilled in the artthat a number of variations and modifications can be made withoutdeparting from the scope of the invention as described herein.

What is claimed is:
 1. A tank comprising: a single tank body made as asingle piece of a composite material using a closed molding process witha first portion of the tank body having an outside surface correspondingto a first molding surface of a first mold and a second portion of thetank body having an outside surface corresponding to a second moldingsurface of a second mold, the tank body having an opening disposedtherein with the opening being substantially smaller than the tank body;and, a fitting member adapted for covering the opening and having aflange, the flange being mounted to a portion of the tank bodysurrounding the opening, wherein the composite material comprises atleast a layer of fiber glass material, and wherein a first layer of thefiber glass material overlaps a second layer of the fiberglass materiala predetermined distance.
 2. The tank according to claim 1 wherein thefirst layer of the fiber glass material is disposed in the first portionof the tank body and the second layer of the fiber glass material isdisposed in the second portion of the tank body.
 3. The tank accordingto claim 1 wherein each of the first portion and the second portion ofthe tank body comprise a portion of the opening.
 4. The tank accordingto claim 1 wherein the fitting member is mounted to an inside surface ofthe tank.
 5. The tank according to claim 1 comprising a base membermounted to a bottom portion of the tank.
 6. A tank comprising: a tankbody, the tank body being a single continuous piece composite materialstructure with: a first portion of the outside surface of the tank bodyhaving a shape corresponding to a molding surface of a first mold; asecond portion of the outside surface of the tank body having a shapecorresponding to a molding surface of a second mold; and a seamconnecting the first portion of the outside surface and the secondportion of the outside surface, the tank body having an opening disposedtherein with the opening being substantially smaller than the tank body;and, a fitting member adapted for covering the opening and having aflange, the flange being mounted to a portion of the tank bodysurrounding the opening.